refactor: Use haumea for filesystem-based module system for flake outputs

refactor: Use hyphen(`-`) for variable names & folder names(except Python), replace all unserscore(`_`) with hyphen(`-`).

outputs/riscv64-linux/default.nix

@@ -0,0 +1,38 @@
+{
+  lib,
+  inputs,
+  ...
+} @ args: let
+  inherit (inputs) haumea;
+
+  # Contains all the flake outputs of this system architecture.
+  data = haumea.lib.load {
+    src = ./src;
+    inputs = args;
+  };
+  # nix file names is redundant, so we remove it.
+  dataWithoutPaths = builtins.attrValues data;
+
+  # Merge all the machine's data into a single attribute set.
+  outputs = {
+    nixosConfigurations = lib.attrsets.mergeAttrsList (map (it: it.nixosConfigurations or {}) dataWithoutPaths);
+    packages = lib.attrsets.mergeAttrsList (map (it: it.packages or {}) dataWithoutPaths);
+    # colmena contains some meta info, which need to be merged carefully.
+    colmena-meta = {
+      nodeNixpkgs = lib.attrsets.mergeAttrsList (map (it: it.colmena-meta.nodeNixpkgs or {}) dataWithoutPaths);
+      nodeSpecialArgs = lib.attrsets.mergeAttrsList (map (it: it.colmena-meta.nodeSpecialArgs or {}) dataWithoutPaths);
+    };
+    # colmena's per-machine data.
+    colmena = lib.attrsets.mergeAttrsList (map (it: it.colmena or {}) dataWithoutPaths);
+  };
+in
+  outputs
+  // {
+    inherit data; # for debugging purposes
+
+    # NixOS's unit tests.
+    # unit-tests = haumea.lib.loadEvalTests {
+    #   src = ./tests;
+    #   inputs = args;
+    # };
+  }

outputs/riscv64-linux/src/rolling-girls-nozomi.nix

@@ -0,0 +1,60 @@
+{
+  # NOTE: the args not used in this file CAN NOT be removed!
+  # because haumea pass argument lazily,
+  # and these arguments are used in the functions like `mylib.nixosSystem`, `mylib.colmenaSystem`, etc.
+  inputs,
+  lib,
+  mylib,
+  myvars,
+  system,
+  genSpecialArgs,
+  ...
+} @ args: let
+  # 森友 望未, Moritomo Nozomi
+  name = "nozomi";
+  tags = [name "riscv"];
+  ssh-user = "root";
+
+  modules = {
+    nixos-modules =
+      (map mylib.relativeToRoot [
+        "modules/nixos/server/server-riscv64.nix"
+        # host specific modules
+        "hosts/rolling-girls-${name}"
+      ])
+      ++ [
+        # cross-compilation this flake.
+        {nixpkgs.crossSystem.system = "riscv64-linux";}
+      ];
+  };
+
+  inherit (inputs) nixos-licheepi4a;
+  baseSpecialArgs = genSpecialArgs system;
+
+  # using the same nixpkgs as nixos-licheepi4a to utilize the cross-compilation cache.
+  lpi4aPkgs = import nixos-licheepi4a.inputs.nixpkgs {inherit system;};
+  lpi4aSpecialArgs =
+    baseSpecialArgs
+    // {
+      inherit (nixos-licheepi4a.inputs) nixpkgs;
+      pkgsKernel = nixos-licheepi4a.packages.${system}.pkgsKernelCross;
+    }
+    // args;
+  lpi4aSystemArgs =
+    modules
+    // args
+    // {
+      inherit (nixos-licheepi4a.inputs) nixpkgs;
+      specialArgs = lpi4aSpecialArgs;
+    };
+in {
+  nixosConfigurations.${name} = mylib.nixosSystem lpi4aSystemArgs;
+
+  colmena-meta = {
+    nodeSpecialArgs.${name} = lpi4aSpecialArgs;
+    nodeNixpkgs.${name} = lpi4aPkgs;
+  };
+  colmena.${name} =
+    mylib.colmenaSystem
+    (lpi4aSystemArgs // {inherit tags ssh-user;});
+}

outputs/riscv64-linux/src/rolling-girls-yukina.nix

@@ -0,0 +1,60 @@
+{
+  # NOTE: the args not used in this file CAN NOT be removed!
+  # because haumea pass argument lazily,
+  # and these arguments are used in the functions like `mylib.nixosSystem`, `mylib.colmenaSystem`, etc.
+  inputs,
+  lib,
+  mylib,
+  myvars,
+  system,
+  genSpecialArgs,
+  ...
+} @ args: let
+  # 小坂 結季奈, Kosaka Yukina
+  name = "yukina";
+  tags = [name "riscv"];
+  ssh-user = "root";
+
+  modules = {
+    nixos-modules =
+      (map mylib.relativeToRoot [
+        "modules/nixos/server/server-riscv64.nix"
+        # host specific modules
+        "hosts/rolling-girls-${name}"
+      ])
+      ++ [
+        # cross-compilation this flake.
+        {nixpkgs.crossSystem.system = "riscv64-linux";}
+      ];
+  };
+
+  inherit (inputs) nixos-licheepi4a;
+  baseSpecialArgs = genSpecialArgs system;
+
+  # using the same nixpkgs as nixos-licheepi4a to utilize the cross-compilation cache.
+  lpi4aPkgs = import nixos-licheepi4a.inputs.nixpkgs {inherit system;};
+  lpi4aSpecialArgs =
+    baseSpecialArgs
+    // {
+      inherit (nixos-licheepi4a.inputs) nixpkgs;
+      pkgsKernel = nixos-licheepi4a.packages.${system}.pkgsKernelCross;
+    }
+    // args;
+  lpi4aSystemArgs =
+    modules
+    // args
+    // {
+      inherit (nixos-licheepi4a.inputs) nixpkgs;
+      specialArgs = lpi4aSpecialArgs;
+    };
+in {
+  nixosConfigurations.${name} = mylib.nixosSystem lpi4aSystemArgs;
+
+  colmena-meta = {
+    nodeSpecialArgs.${name} = lpi4aSpecialArgs;
+    nodeNixpkgs.${name} = lpi4aPkgs;
+  };
+  colmena.${name} =
+    mylib.colmenaSystem
+    (lpi4aSystemArgs // {inherit tags ssh-user;});
+}